// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Platform-specific code for POSIX goes here. This is not a platform on its
// own, but contains the parts which are the same across the POSIX platforms
// Linux, MacOS, FreeBSD, OpenBSD, NetBSD and QNX.

#include <errno.h>
#include <limits.h>
#include <pthread.h>
#if defined(__DragonFly__) || defined(__FreeBSD__) || defined(__OpenBSD__)
#include <pthread_np.h> // for pthread_set_name_np
#endif
#include <sched.h> // for sched_yield
#include <stdio.h>
#include <time.h>
#include <unistd.h>

#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#if defined(__APPLE__) || defined(__DragonFly__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
#include <sys/sysctl.h> // NOLINT, for sysctl
#endif

#if defined(ANDROID) && !defined(V8_ANDROID_LOG_STDOUT)
#define LOG_TAG "v8"
#include <android/log.h> // NOLINT
#endif

#include <cmath>
#include <cstdlib>

#include "src/base/platform/platform-posix.h"

#include "src/base/lazy-instance.h"
#include "src/base/macros.h"
#include "src/base/platform/platform.h"
#include "src/base/platform/time.h"
#include "src/base/utils/random-number-generator.h"

#ifdef V8_FAST_TLS_SUPPORTED
#include <atomic>
#endif

#if V8_OS_MACOSX
#include <dlfcn.h>
#endif

#if V8_OS_LINUX
#include <sys/prctl.h> // NOLINT, for prctl
#endif

#if defined(V8_OS_FUCHSIA)
#include <zircon/process.h>
#else
#include <sys/resource.h>
#endif

#if !defined(_AIX) && !defined(V8_OS_FUCHSIA)
#include <sys/syscall.h>
#endif

#if V8_OS_FREEBSD || V8_OS_MACOSX || V8_OS_OPENBSD || V8_OS_SOLARIS
#define MAP_ANONYMOUS MAP_ANON
#endif

#if defined(V8_OS_SOLARIS)
#if (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE > 2) || defined(__EXTENSIONS__)
extern "C" int madvise(caddr_t, size_t, int);
#else
extern int madvise(caddr_t, size_t, int);
#endif
#endif

#ifndef MADV_FREE
#define MADV_FREE MADV_DONTNEED
#endif

namespace v8 {
namespace base {

    namespace {

        // 0 is never a valid thread id.
        const pthread_t kNoThread = static_cast<pthread_t>(0);

        bool g_hard_abort = false;

        const char* g_gc_fake_mmap = nullptr;

        DEFINE_LAZY_LEAKY_OBJECT_GETTER(RandomNumberGenerator,
            GetPlatformRandomNumberGenerator)
        static LazyMutex rng_mutex = LAZY_MUTEX_INITIALIZER;

#if !V8_OS_FUCHSIA
#if V8_OS_MACOSX
        // kMmapFd is used to pass vm_alloc flags to tag the region with the user
        // defined tag 255 This helps identify V8-allocated regions in memory analysis
        // tools like vmmap(1).
        const int kMmapFd = VM_MAKE_TAG(255);
#else // !V8_OS_MACOSX
        const int kMmapFd = -1;
#endif // !V8_OS_MACOSX

        const int kMmapFdOffset = 0;

        int GetProtectionFromMemoryPermission(OS::MemoryPermission access)
        {
            switch (access) {
            case OS::MemoryPermission::kNoAccess:
                return PROT_NONE;
            case OS::MemoryPermission::kRead:
                return PROT_READ;
            case OS::MemoryPermission::kReadWrite:
                return PROT_READ | PROT_WRITE;
            case OS::MemoryPermission::kReadWriteExecute:
                return PROT_READ | PROT_WRITE | PROT_EXEC;
            case OS::MemoryPermission::kReadExecute:
                return PROT_READ | PROT_EXEC;
            }
            UNREACHABLE();
        }

        int GetFlagsForMemoryPermission(OS::MemoryPermission access)
        {
            int flags = MAP_PRIVATE | MAP_ANONYMOUS;
            if (access == OS::MemoryPermission::kNoAccess) {
#if !V8_OS_AIX && !V8_OS_FREEBSD && !V8_OS_QNX
                flags |= MAP_NORESERVE;
#endif // !V8_OS_AIX && !V8_OS_FREEBSD && !V8_OS_QNX
#if V8_OS_QNX
                flags |= MAP_LAZY;
#endif // V8_OS_QNX
            }
            return flags;
        }

        void* Allocate(void* address, size_t size, OS::MemoryPermission access)
        {
            int prot = GetProtectionFromMemoryPermission(access);
            int flags = GetFlagsForMemoryPermission(access);
            void* result = mmap(address, size, prot, flags, kMmapFd, kMmapFdOffset);
            if (result == MAP_FAILED)
                return nullptr;
            return result;
        }

#endif // !V8_OS_FUCHSIA

    } // namespace

    void OS::Initialize(bool hard_abort, const char* const gc_fake_mmap)
    {
        g_hard_abort = hard_abort;
        g_gc_fake_mmap = gc_fake_mmap;
    }

    int OS::ActivationFrameAlignment()
    {
#if V8_TARGET_ARCH_ARM
        // On EABI ARM targets this is required for fp correctness in the
        // runtime system.
        return 8;
#elif V8_TARGET_ARCH_MIPS
        return 8;
#elif V8_TARGET_ARCH_S390
        return 8;
#else
        // Otherwise we just assume 16 byte alignment, i.e.:
        // - With gcc 4.4 the tree vectorization optimizer can generate code
        //   that requires 16 byte alignment such as movdqa on x86.
        // - Mac OS X, PPC and Solaris (64-bit) activation frames must
        //   be 16 byte-aligned;  see "Mac OS X ABI Function Call Guide"
        return 16;
#endif
    }

    // static
    size_t OS::AllocatePageSize()
    {
        return static_cast<size_t>(sysconf(_SC_PAGESIZE));
    }

    // static
    size_t OS::CommitPageSize()
    {
        static size_t page_size = getpagesize();
        return page_size;
    }

    // static
    void OS::SetRandomMmapSeed(int64_t seed)
    {
        if (seed) {
            MutexGuard guard(rng_mutex.Pointer());
            GetPlatformRandomNumberGenerator()->SetSeed(seed);
        }
    }

    // static
    void* OS::GetRandomMmapAddr()
    {
        uintptr_t raw_addr;
        {
            MutexGuard guard(rng_mutex.Pointer());
            GetPlatformRandomNumberGenerator()->NextBytes(&raw_addr, sizeof(raw_addr));
        }
#if defined(V8_USE_ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || defined(THREAD_SANITIZER) || defined(LEAK_SANITIZER)
        // If random hint addresses interfere with address ranges hard coded in
        // sanitizers, bad things happen. This address range is copied from TSAN
        // source but works with all tools.
        // See crbug.com/539863.
        raw_addr &= 0x007fffff0000ULL;
        raw_addr += 0x7e8000000000ULL;
#else
#if V8_TARGET_ARCH_X64
        // Currently available CPUs have 48 bits of virtual addressing.  Truncate
        // the hint address to 46 bits to give the kernel a fighting chance of
        // fulfilling our placement request.
        raw_addr &= uint64_t { 0x3FFFFFFFF000 };
#elif V8_TARGET_ARCH_PPC64
#if V8_OS_AIX
        // AIX: 64 bits of virtual addressing, but we limit address range to:
        //   a) minimize Segment Lookaside Buffer (SLB) misses and
        raw_addr &= uint64_t { 0x3FFFF000 };
        // Use extra address space to isolate the mmap regions.
        raw_addr += uint64_t { 0x400000000000 };
#elif V8_TARGET_BIG_ENDIAN
        // Big-endian Linux: 42 bits of virtual addressing.
        raw_addr &= uint64_t { 0x03FFFFFFF000 };
#else
        // Little-endian Linux: 46 bits of virtual addressing.
        raw_addr &= uint64_t { 0x3FFFFFFF0000 };
#endif
#elif V8_TARGET_ARCH_S390X
        // Linux on Z uses bits 22-32 for Region Indexing, which translates to 42 bits
        // of virtual addressing.  Truncate to 40 bits to allow kernel chance to
        // fulfill request.
        raw_addr &= uint64_t { 0xFFFFFFF000 };
#elif V8_TARGET_ARCH_S390
        // 31 bits of virtual addressing.  Truncate to 29 bits to allow kernel chance
        // to fulfill request.
        raw_addr &= 0x1FFFF000;
#elif V8_TARGET_ARCH_MIPS64
        // 42 bits of virtual addressing. Truncate to 40 bits to allow kernel chance
        // to fulfill request.
        raw_addr &= uint64_t { 0xFFFFFF0000 };
#else
        raw_addr &= 0x3FFFF000;

#ifdef __sun
        // For our Solaris/illumos mmap hint, we pick a random address in the bottom
        // half of the top half of the address space (that is, the third quarter).
        // Because we do not MAP_FIXED, this will be treated only as a hint -- the
        // system will not fail to mmap() because something else happens to already
        // be mapped at our random address. We deliberately set the hint high enough
        // to get well above the system's break (that is, the heap); Solaris and
        // illumos will try the hint and if that fails allocate as if there were
        // no hint at all. The high hint prevents the break from getting hemmed in
        // at low values, ceding half of the address space to the system heap.
        raw_addr += 0x80000000;
#elif V8_OS_AIX
        // The range 0x30000000 - 0xD0000000 is available on AIX;
        // choose the upper range.
        raw_addr += 0x90000000;
#else
        // The range 0x20000000 - 0x60000000 is relatively unpopulated across a
        // variety of ASLR modes (PAE kernel, NX compat mode, etc) and on macos
        // 10.6 and 10.7.
        raw_addr += 0x20000000;
#endif
#endif
#endif
        return reinterpret_cast<void*>(raw_addr);
    }

// TODO(bbudge) Move Cygwin and Fuchsia stuff into platform-specific files.
#if !V8_OS_CYGWIN && !V8_OS_FUCHSIA
    // static
    void* OS::Allocate(void* address, size_t size, size_t alignment,
        MemoryPermission access)
    {
        size_t page_size = AllocatePageSize();
        DCHECK_EQ(0, size % page_size);
        DCHECK_EQ(0, alignment % page_size);
        address = AlignedAddress(address, alignment);
        // Add the maximum misalignment so we are guaranteed an aligned base address.
        size_t request_size = size + (alignment - page_size);
        request_size = RoundUp(request_size, OS::AllocatePageSize());
        void* result = base::Allocate(address, request_size, access);
        if (result == nullptr)
            return nullptr;

        // Unmap memory allocated before the aligned base address.
        uint8_t* base = static_cast<uint8_t*>(result);
        uint8_t* aligned_base = reinterpret_cast<uint8_t*>(
            RoundUp(reinterpret_cast<uintptr_t>(base), alignment));
        if (aligned_base != base) {
            DCHECK_LT(base, aligned_base);
            size_t prefix_size = static_cast<size_t>(aligned_base - base);
            CHECK(Free(base, prefix_size));
            request_size -= prefix_size;
        }
        // Unmap memory allocated after the potentially unaligned end.
        if (size != request_size) {
            DCHECK_LT(size, request_size);
            size_t suffix_size = request_size - size;
            CHECK(Free(aligned_base + size, suffix_size));
            request_size -= suffix_size;
        }

        DCHECK_EQ(size, request_size);
        return static_cast<void*>(aligned_base);
    }

    // static
    bool OS::Free(void* address, const size_t size)
    {
        DCHECK_EQ(0, reinterpret_cast<uintptr_t>(address) % AllocatePageSize());
        DCHECK_EQ(0, size % AllocatePageSize());
        return munmap(address, size) == 0;
    }

    // static
    bool OS::Release(void* address, size_t size)
    {
        DCHECK_EQ(0, reinterpret_cast<uintptr_t>(address) % CommitPageSize());
        DCHECK_EQ(0, size % CommitPageSize());
        return munmap(address, size) == 0;
    }

    // static
    bool OS::SetPermissions(void* address, size_t size, MemoryPermission access)
    {
        DCHECK_EQ(0, reinterpret_cast<uintptr_t>(address) % CommitPageSize());
        DCHECK_EQ(0, size % CommitPageSize());

        int prot = GetProtectionFromMemoryPermission(access);
        int ret = mprotect(address, size, prot);
        if (ret == 0 && access == OS::MemoryPermission::kNoAccess) {
            // This is advisory; ignore errors and continue execution.
            USE(DiscardSystemPages(address, size));
        }

// For accounting purposes, we want to call MADV_FREE_REUSE on macOS after
// changing permissions away from OS::MemoryPermission::kNoAccess. Since this
// state is not kept at this layer, we always call this if access != kNoAccess.
// The cost is a syscall that effectively no-ops.
// TODO(erikchen): Fix this to only call MADV_FREE_REUSE when necessary.
// https://crbug.com/823915
#if defined(OS_MACOSX)
        if (access != OS::MemoryPermission::kNoAccess)
            madvise(address, size, MADV_FREE_REUSE);
#endif

        return ret == 0;
    }

    bool OS::DiscardSystemPages(void* address, size_t size)
    {
        DCHECK_EQ(0, reinterpret_cast<uintptr_t>(address) % CommitPageSize());
        DCHECK_EQ(0, size % CommitPageSize());
#if defined(OS_MACOSX)
        // On OSX, MADV_FREE_REUSABLE has comparable behavior to MADV_FREE, but also
        // marks the pages with the reusable bit, which allows both Activity Monitor
        // and memory-infra to correctly track the pages.
        int ret = madvise(address, size, MADV_FREE_REUSABLE);
#elif defined(_AIX) || defined(V8_OS_SOLARIS)
        int ret = madvise(reinterpret_cast<caddr_t>(address), size, MADV_FREE);
#else
        int ret = madvise(address, size, MADV_FREE);
#endif
        if (ret != 0 && errno == ENOSYS)
            return true; // madvise is not available on all systems.
        if (ret != 0 && errno == EINVAL) {
// MADV_FREE only works on Linux 4.5+ . If request failed, retry with older
// MADV_DONTNEED . Note that MADV_FREE being defined at compile time doesn't
// imply runtime support.
#if defined(_AIX) || defined(V8_OS_SOLARIS)
            ret = madvise(reinterpret_cast<caddr_t>(address), size, MADV_DONTNEED);
#else
            ret = madvise(address, size, MADV_DONTNEED);
#endif
        }
        return ret == 0;
    }

    // static
    bool OS::HasLazyCommits()
    {
#if V8_OS_AIX || V8_OS_LINUX || V8_OS_MACOSX
        return true;
#else
        // TODO(bbudge) Return true for all POSIX platforms.
        return false;
#endif
    }
#endif // !V8_OS_CYGWIN && !V8_OS_FUCHSIA

    const char* OS::GetGCFakeMMapFile()
    {
        return g_gc_fake_mmap;
    }

    void OS::Sleep(TimeDelta interval)
    {
        usleep(static_cast<useconds_t>(interval.InMicroseconds()));
    }

    void OS::Abort()
    {
        if (g_hard_abort) {
            V8_IMMEDIATE_CRASH();
        }
        // Redirect to std abort to signal abnormal program termination.
        abort();
    }

    void OS::DebugBreak()
    {
#if V8_HOST_ARCH_ARM
        asm("bkpt 0");
#elif V8_HOST_ARCH_ARM64
        asm("brk 0");
#elif V8_HOST_ARCH_MIPS
        asm("break");
#elif V8_HOST_ARCH_MIPS64
        asm("break");
#elif V8_HOST_ARCH_PPC
        asm("twge 2,2");
#elif V8_HOST_ARCH_IA32
        asm("int $3");
#elif V8_HOST_ARCH_X64
        asm("int $3");
#elif V8_HOST_ARCH_S390
        // Software breakpoint instruction is 0x0001
        asm volatile(".word 0x0001");
#else
#error Unsupported host architecture.
#endif
    }

    class PosixMemoryMappedFile final : public OS::MemoryMappedFile {
    public:
        PosixMemoryMappedFile(FILE* file, void* memory, size_t size)
            : file_(file)
            , memory_(memory)
            , size_(size)
        {
        }
        ~PosixMemoryMappedFile() final;
        void* memory() const final { return memory_; }
        size_t size() const final { return size_; }

    private:
        FILE* const file_;
        void* const memory_;
        size_t const size_;
    };

    // static
    OS::MemoryMappedFile* OS::MemoryMappedFile::open(const char* name,
        FileMode mode)
    {
        const char* fopen_mode = (mode == FileMode::kReadOnly) ? "r" : "r+";
        if (FILE* file = fopen(name, fopen_mode)) {
            if (fseek(file, 0, SEEK_END) == 0) {
                long size = ftell(file); // NOLINT(runtime/int)
                if (size == 0)
                    return new PosixMemoryMappedFile(file, nullptr, 0);
                if (size > 0) {
                    int prot = PROT_READ;
                    int flags = MAP_PRIVATE;
                    if (mode == FileMode::kReadWrite) {
                        prot |= PROT_WRITE;
                        flags = MAP_SHARED;
                    }
                    void* const memory = mmap(OS::GetRandomMmapAddr(), size, prot, flags, fileno(file), 0);
                    if (memory != MAP_FAILED) {
                        return new PosixMemoryMappedFile(file, memory, size);
                    }
                }
            }
            fclose(file);
        }
        return nullptr;
    }

    // static
    OS::MemoryMappedFile* OS::MemoryMappedFile::create(const char* name,
        size_t size, void* initial)
    {
        if (FILE* file = fopen(name, "w+")) {
            if (size == 0)
                return new PosixMemoryMappedFile(file, 0, 0);
            size_t result = fwrite(initial, 1, size, file);
            if (result == size && !ferror(file)) {
                void* memory = mmap(OS::GetRandomMmapAddr(), result,
                    PROT_READ | PROT_WRITE, MAP_SHARED, fileno(file), 0);
                if (memory != MAP_FAILED) {
                    return new PosixMemoryMappedFile(file, memory, result);
                }
            }
            fclose(file);
        }
        return nullptr;
    }

    PosixMemoryMappedFile::~PosixMemoryMappedFile()
    {
        if (memory_)
            CHECK(OS::Free(memory_, RoundUp(size_, OS::AllocatePageSize())));
        fclose(file_);
    }

    int OS::GetCurrentProcessId()
    {
        return static_cast<int>(getpid());
    }

    int OS::GetCurrentThreadId()
    {
#if V8_OS_MACOSX || (V8_OS_ANDROID && defined(__APPLE__))
        return static_cast<int>(pthread_mach_thread_np(pthread_self()));
#elif V8_OS_LINUX
        return static_cast<int>(syscall(__NR_gettid));
#elif V8_OS_ANDROID
        return static_cast<int>(gettid());
#elif V8_OS_AIX
        return static_cast<int>(thread_self());
#elif V8_OS_FUCHSIA
        return static_cast<int>(zx_thread_self());
#elif V8_OS_SOLARIS
        return static_cast<int>(pthread_self());
#else
        return static_cast<int>(reinterpret_cast<intptr_t>(pthread_self()));
#endif
    }

    void OS::ExitProcess(int exit_code)
    {
        // Use _exit instead of exit to avoid races between isolate
        // threads and static destructors.
        fflush(stdout);
        fflush(stderr);
        _exit(exit_code);
    }

    // ----------------------------------------------------------------------------
    // POSIX date/time support.
    //

#if !defined(V8_OS_FUCHSIA)
    int OS::GetUserTime(uint32_t* secs, uint32_t* usecs)
    {
        struct rusage usage;

        if (getrusage(RUSAGE_SELF, &usage) < 0)
            return -1;
        *secs = static_cast<uint32_t>(usage.ru_utime.tv_sec);
        *usecs = static_cast<uint32_t>(usage.ru_utime.tv_usec);
        return 0;
    }
#endif

    double OS::TimeCurrentMillis()
    {
        return Time::Now().ToJsTime();
    }

    double PosixTimezoneCache::DaylightSavingsOffset(double time)
    {
        if (/*std::*/isnan(time))
            return std::numeric_limits<double>::quiet_NaN();
        time_t tv = static_cast<time_t>(std::floor(time / msPerSecond));
        struct tm tm;
        struct tm* t = localtime_r(&tv, &tm);
        if (nullptr == t)
            return std::numeric_limits<double>::quiet_NaN();
        return t->tm_isdst > 0 ? 3600 * msPerSecond : 0;
    }

    int OS::GetLastError()
    {
        return errno;
    }

    // ----------------------------------------------------------------------------
    // POSIX stdio support.
    //

    FILE* OS::FOpen(const char* path, const char* mode)
    {
        FILE* file = fopen(path, mode);
        if (file == nullptr)
            return nullptr;
        struct stat file_stat;
        if (fstat(fileno(file), &file_stat) != 0) {
            fclose(file);
            return nullptr;
        }
        bool is_regular_file = ((file_stat.st_mode & S_IFREG) != 0);
        if (is_regular_file)
            return file;
        fclose(file);
        return nullptr;
    }

    bool OS::Remove(const char* path)
    {
        return (remove(path) == 0);
    }

    char OS::DirectorySeparator() { return '/'; }

    bool OS::isDirectorySeparator(const char ch)
    {
        return ch == DirectorySeparator();
    }

    FILE* OS::OpenTemporaryFile()
    {
        return tmpfile();
    }

    const char* const OS::LogFileOpenMode = "w";

    void OS::Print(const char* format, ...)
    {
        va_list args;
        va_start(args, format);
        VPrint(format, args);
        va_end(args);
    }

    void OS::VPrint(const char* format, va_list args)
    {
#if defined(ANDROID) && !defined(V8_ANDROID_LOG_STDOUT)
        __android_log_vprint(ANDROID_LOG_INFO, LOG_TAG, format, args);
#else
        vprintf(format, args);
#endif
    }

    void OS::FPrint(FILE* out, const char* format, ...)
    {
        va_list args;
        va_start(args, format);
        VFPrint(out, format, args);
        va_end(args);
    }

    void OS::VFPrint(FILE* out, const char* format, va_list args)
    {
#if defined(ANDROID) && !defined(V8_ANDROID_LOG_STDOUT)
        __android_log_vprint(ANDROID_LOG_INFO, LOG_TAG, format, args);
#else
        vfprintf(out, format, args);
#endif
    }

    void OS::PrintError(const char* format, ...)
    {
        va_list args;
        va_start(args, format);
        VPrintError(format, args);
        va_end(args);
    }

    void OS::VPrintError(const char* format, va_list args)
    {
#if defined(ANDROID) && !defined(V8_ANDROID_LOG_STDOUT)
        __android_log_vprint(ANDROID_LOG_ERROR, LOG_TAG, format, args);
#else
        vfprintf(stderr, format, args);
#endif
    }

    int OS::SNPrintF(char* str, int length, const char* format, ...)
    {
        va_list args;
        va_start(args, format);
        int result = VSNPrintF(str, length, format, args);
        va_end(args);
        return result;
    }

    int OS::VSNPrintF(char* str,
        int length,
        const char* format,
        va_list args)
    {
        int n = vsnprintf(str, length, format, args);
        if (n < 0 || n >= length) {
            // If the length is zero, the assignment fails.
            if (length > 0)
                str[length - 1] = '\0';
            return -1;
        } else {
            return n;
        }
    }

    // ----------------------------------------------------------------------------
    // POSIX string support.
    //

    char* OS::StrChr(char* str, int c)
    {
        return strchr(str, c);
    }

    void OS::StrNCpy(char* dest, int length, const char* src, size_t n)
    {
        strncpy(dest, src, n);
    }

    // ----------------------------------------------------------------------------
    // POSIX thread support.
    //

    class Thread::PlatformData {
    public:
        PlatformData()
            : thread_(kNoThread)
        {
        }
        pthread_t thread_; // Thread handle for pthread.
        // Synchronizes thread creation
        Mutex thread_creation_mutex_;
    };

    Thread::Thread(const Options& options)
        : data_(new PlatformData)
        , stack_size_(options.stack_size())
        , start_semaphore_(nullptr)
    {
        if (stack_size_ > 0 && static_cast<size_t>(stack_size_) < PTHREAD_STACK_MIN) {
            stack_size_ = PTHREAD_STACK_MIN;
        }
        set_name(options.name());
    }

    Thread::~Thread()
    {
        delete data_;
    }

    static void SetThreadName(const char* name)
    {
#if V8_OS_DRAGONFLYBSD || V8_OS_FREEBSD || V8_OS_OPENBSD
        pthread_set_name_np(pthread_self(), name);
#elif V8_OS_NETBSD
        STATIC_ASSERT(Thread::kMaxThreadNameLength <= PTHREAD_MAX_NAMELEN_NP);
        pthread_setname_np(pthread_self(), "%s", name);
#elif V8_OS_MACOSX
        // pthread_setname_np is only available in 10.6 or later, so test
        // for it at runtime.
        int (*dynamic_pthread_setname_np)(const char*);
        *reinterpret_cast<void**>(&dynamic_pthread_setname_np) = dlsym(RTLD_DEFAULT, "pthread_setname_np");
        if (dynamic_pthread_setname_np == nullptr)
            return;

        // Mac OS X does not expose the length limit of the name, so hardcode it.
        static const int kMaxNameLength = 63;
        STATIC_ASSERT(Thread::kMaxThreadNameLength <= kMaxNameLength);
        dynamic_pthread_setname_np(name);
#elif defined(PR_SET_NAME)
        prctl(PR_SET_NAME,
            reinterpret_cast<unsigned long>(name), // NOLINT
            0, 0, 0);
#endif
    }

    static void* ThreadEntry(void* arg)
    {
        Thread* thread = reinterpret_cast<Thread*>(arg);
        // We take the lock here to make sure that pthread_create finished first since
        // we don't know which thread will run first (the original thread or the new
        // one).
        {
            MutexGuard lock_guard(&thread->data()->thread_creation_mutex_);
        }
        SetThreadName(thread->name());
        DCHECK_NE(thread->data()->thread_, kNoThread);
        thread->NotifyStartedAndRun();
        return nullptr;
    }

    void Thread::set_name(const char* name)
    {
        strncpy(name_, name, sizeof(name_));
        name_[sizeof(name_) - 1] = '\0';
    }

    void Thread::Start()
    {
        int result;
        pthread_attr_t attr;
        memset(&attr, 0, sizeof(attr));
        result = pthread_attr_init(&attr);
        DCHECK_EQ(0, result);
        size_t stack_size = stack_size_;
        if (stack_size == 0) {
#if V8_OS_MACOSX
            // Default on Mac OS X is 512kB -- bump up to 1MB
            stack_size = 1 * 1024 * 1024;
#elif V8_OS_AIX
            // Default on AIX is 96kB -- bump up to 2MB
            stack_size = 2 * 1024 * 1024;
#endif
        }
        if (stack_size > 0) {
            result = pthread_attr_setstacksize(&attr, stack_size);
            DCHECK_EQ(0, result);
        }
        {
            MutexGuard lock_guard(&data_->thread_creation_mutex_);
            result = pthread_create(&data_->thread_, &attr, ThreadEntry, this);
        }
        DCHECK_EQ(0, result);
        result = pthread_attr_destroy(&attr);
        DCHECK_EQ(0, result);
        DCHECK_NE(data_->thread_, kNoThread);
        USE(result);
    }

    void Thread::Join() { pthread_join(data_->thread_, nullptr); }

    static Thread::LocalStorageKey PthreadKeyToLocalKey(pthread_key_t pthread_key)
    {
#if V8_OS_CYGWIN
        // We need to cast pthread_key_t to Thread::LocalStorageKey in two steps
        // because pthread_key_t is a pointer type on Cygwin. This will probably not
        // work on 64-bit platforms, but Cygwin doesn't support 64-bit anyway.
        STATIC_ASSERT(sizeof(Thread::LocalStorageKey) == sizeof(pthread_key_t));
        intptr_t ptr_key = reinterpret_cast<intptr_t>(pthread_key);
        return static_cast<Thread::LocalStorageKey>(ptr_key);
#else
        return static_cast<Thread::LocalStorageKey>(pthread_key);
#endif
    }

    static pthread_key_t LocalKeyToPthreadKey(Thread::LocalStorageKey local_key)
    {
#if V8_OS_CYGWIN
        STATIC_ASSERT(sizeof(Thread::LocalStorageKey) == sizeof(pthread_key_t));
        intptr_t ptr_key = static_cast<intptr_t>(local_key);
        return reinterpret_cast<pthread_key_t>(ptr_key);
#else
        return static_cast<pthread_key_t>(local_key);
#endif
    }

#ifdef V8_FAST_TLS_SUPPORTED

    static std::atomic<bool> tls_base_offset_initialized { false };
    intptr_t kMacTlsBaseOffset = 0;

    // It's safe to do the initialization more that once, but it has to be
    // done at least once.
    static void InitializeTlsBaseOffset()
    {
        const size_t kBufferSize = 128;
        char buffer[kBufferSize];
        size_t buffer_size = kBufferSize;
        int ctl_name[] = { CTL_KERN, KERN_OSRELEASE };
        if (sysctl(ctl_name, 2, buffer, &buffer_size, nullptr, 0) != 0) {
            FATAL("V8 failed to get kernel version");
        }
        // The buffer now contains a string of the form XX.YY.ZZ, where
        // XX is the major kernel version component.
        // Make sure the buffer is 0-terminated.
        buffer[kBufferSize - 1] = '\0';
        char* period_pos = strchr(buffer, '.');
        *period_pos = '\0';
        int kernel_version_major = static_cast<int>(strtol(buffer, nullptr, 10)); // NOLINT
        // The constants below are taken from pthreads.s from the XNU kernel
        // sources archive at www.opensource.apple.com.
        if (kernel_version_major < 11) {
            // 8.x.x (Tiger), 9.x.x (Leopard), 10.x.x (Snow Leopard) have the
            // same offsets.
#if V8_HOST_ARCH_IA32
            kMacTlsBaseOffset = 0x48;
#else
            kMacTlsBaseOffset = 0x60;
#endif
        } else {
            // 11.x.x (Lion) changed the offset.
            kMacTlsBaseOffset = 0;
        }

        tls_base_offset_initialized.store(true, std::memory_order_release);
    }

    static void CheckFastTls(Thread::LocalStorageKey key)
    {
        void* expected = reinterpret_cast<void*>(0x1234CAFE);
        Thread::SetThreadLocal(key, expected);
        void* actual = Thread::GetExistingThreadLocal(key);
        if (expected != actual) {
            FATAL("V8 failed to initialize fast TLS on current kernel");
        }
        Thread::SetThreadLocal(key, nullptr);
    }

#endif // V8_FAST_TLS_SUPPORTED

    Thread::LocalStorageKey Thread::CreateThreadLocalKey()
    {
#ifdef V8_FAST_TLS_SUPPORTED
        bool check_fast_tls = false;
        if (!tls_base_offset_initialized.load(std::memory_order_acquire)) {
            check_fast_tls = true;
            InitializeTlsBaseOffset();
        }
#endif
        pthread_key_t key;
        int result = pthread_key_create(&key, nullptr);
        DCHECK_EQ(0, result);
        USE(result);
        LocalStorageKey local_key = PthreadKeyToLocalKey(key);
#ifdef V8_FAST_TLS_SUPPORTED
        // If we just initialized fast TLS support, make sure it works.
        if (check_fast_tls)
            CheckFastTls(local_key);
#endif
        return local_key;
    }

    void Thread::DeleteThreadLocalKey(LocalStorageKey key)
    {
        pthread_key_t pthread_key = LocalKeyToPthreadKey(key);
        int result = pthread_key_delete(pthread_key);
        DCHECK_EQ(0, result);
        USE(result);
    }

    void* Thread::GetThreadLocal(LocalStorageKey key)
    {
        pthread_key_t pthread_key = LocalKeyToPthreadKey(key);
        return pthread_getspecific(pthread_key);
    }

    void Thread::SetThreadLocal(LocalStorageKey key, void* value)
    {
        pthread_key_t pthread_key = LocalKeyToPthreadKey(key);
        int result = pthread_setspecific(pthread_key, value);
        DCHECK_EQ(0, result);
        USE(result);
    }

#undef LOG_TAG
#undef MAP_ANONYMOUS
#undef MADV_FREE

} // namespace base
} // namespace v8
